Abstract: A method and system for asserting a lock in a distributed file system is provided. All distributed locks have a lease for a limited time period, wherein the lease may be renewed periodically. A lock manager data structure is provided to maintain mode compatibility of locks granted to different client nodes for the same system object. The process of acquiring (60) or reasserting (140) a lock includes determining whether there are other valid locks in use, as well as whether a valid lock is operation in a conflicting or compatible mode with a requested lock (86, 166). A new lock lease maybe granted (120) and a lock lease which has expired may be reasserted (172) if a conflicting lease is not present.

Abstract: A method and apparatus is provided for measuring and optimizing the orientation of data access of an electronic storage device according to data access characteristics. Monitoring storage access activity in an area of storage space is performed to gather data pertaining to one or more storage access characteristics. Measuring is performed of the characteristics of the storage access activity of at least two individual portions of the storage space. The portions are then combined in a manner to more judiciously utilize storage space. Depending on their homogeneity of access characteristics, the individual portions may then be left alone, merged with other similar portions, or further subdivided into sub-portions, which may be further merged, divided or left alone. At each merger or division determinations can then be made of whether the characteristics of storage access activity of one individual portion or sub-portion are similar to that of another portion according to predetermined criteria.

Abstract: A method and apparatus is provided for measuring and optimizing the orientation of data access of an electronic storage device according to data access characteristics. Monitoring storage access activity in an area of storage space is performed to gather data pertaining to one or more storage access characteristics. Measuring is performed of the characteristics of the storage access activity of at least two individual portions of the storage space. The portions are then combined in a manner to more judiciously utilize storage space. Depending on their homogeneity of access characteristics, the individual portions may then be left alone, merged with other similar portions, or further subdivided into sub-portions, which may be further merged, divided or left alone. At each merger or division determinations can then be made of whether the characteristics of storage access activity of one individual portion or sub-portion are similar to that of another portion according to predetermined criteria.

Abstract: Given a multi-component system and a multi-part performability requirement, a method and apparatus for determining whether the system will satisfy the multi-part performability requirement is described. The method uses a failure-scenario generator that analyzes the most-likely failure scenarios first and operates only until a PASS-FAIL determination can be rendered.

Abstract: A method predicts performance of a system that includes a plurality of interconnected components defining at least one data flow path. The method references a workload specification for the system. The method models the system using one or more component models. Each component model represents selected one or more of the components. Each component model is arranged in like relationship to the data flow path as the selected one or more of the components represented by the component model. Each component model is (a) a constraint upon the workload specification input to that component model or (b) a transformer of the workload specification input to that component model so as to result in one or more output workload specifications that are input workload specifications to subsequent component models along the data flow path or (c) both a constraint and a transformer. At least one of the component models is a constraint.